Oxygen saturation (symbol SO2) is a relative measure of the amount of oxygen that is dissolved or carried in a given medium such as blood. Oxygen saturation is typically measured in percent (%) and is useful to monitor a respective subjects overall oxygen supply and consumption.
Oxygen saturation of blood in a subject can be measured in a number of different ways. For example, conventional techniques include both invasive and noninvasive methods to determine oxygen saturation in blood.
According to conventional invasive techniques, a catheter including an oxygen sensor is inserted (in a subcutaneous manner) into a blood vessel of the respective subject. The oxygen sensor in the catheter in contact with blood generates respective one or more signals. An analyzer analyzes the signals to measure an amount of oxygen in the blood.
Arterial oxygen saturation (SaO2) is commonly measured using so-called pulse oximetry techniques. According to this non-invasive technique, a selected site of the patient under test is exposed to an optical signal. A photo detector detects an intensity of the optical signal transmitted through or reflected off the high-pressure, pulsing blood at the selected site. An analyzer determines an AC component of the absorbance at each wavelength and then divides it by the corresponding DC component to obtain a ratio that is independent of the incident light intensity. The analyzer uses a ratio of the ratios on different wavelengths to determine oxygen content in the artery (media having a pulse). This technique provides the oxygen saturation in the artery (or the capillaries). The signal obtained from pulse oximetry can also be used to measure other parameters of the arterial and capillary networks such as vessel stiffness.